Learning cycles material nodes
You can in theory create any material in the properties editor just as well as the node editor, but in practice the node editor is a lot easier and faster to work with once you get used to it.
Material nodes mostly work by mixing together different aspects of the way a surface interacts with light (shader nodes) and by mixing together different textures, whether they are 3D procedural textures or 2D image textures.
For instance you might mix some diffuse and glossy together based on fresnel node to make a simple ceramic shader:

Or you might use a procedural voronoi texture to add some displacement and make
a kind of hammered copper shader:

The possibilities are pretty much endless.
I'd recommend you look around for some tutorials to get used to working with nodes. There are plenty on youtube and similar sites. Here are some others to get you started:

Blender guru

Blender diplom

Blender cookie


And the manual is a good a reference for information on specific nodes.
And of course you can always ask around here if you have more questions ;)